Noise radiation patterns of counter-rotation and unsteadily loaded single-rotation propellers

Abstract

In order to understand the effects of installation on propeller noise, numerous measurements are required to define the directivity of the noise as well as the level. An experimental study was designed to map the noise radiation pattern for various single-rotation propeller (SRP) installations and one counter-rotation propeller (CRP) installation covering an area ± 60 deg from the propeller disk plane and ± 60 deg laterally. The configurations considered included an SRP at angle of attack and in tractor and pusher operations and a CRP. A firstprinciples linear theory was validated for the SRP tractor operation over the angle range mentioned above. The increases in noise that arise from an unsteady loading operation such as an SRP pusher or a CRP exceed 15 dB and depend on the observer location. In particular, the majority of the additional noise from the unsteady loading appears to radiate in the axial directions.